JP4164923B2 - DC-DC converter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a DC-DC converter.
[0002]
[Prior art]
Conventional DC-DC converters are usually composed of an inverter circuit that forms a single-phase AC voltage formed from an input DC voltage, a transformer that transforms the single-phase AC voltage, a rectifier circuit that rectifies the output voltage of the transformer, and a snubber circuit. ,It is configured.
Usually, the transformer and the rectifier circuit adopt a single-phase full-wave rectification method. For this reason, the transformer has a secondary coil composed of a pair of partial coils wound in the same direction and connected in series. The circuit includes a pair of rectifying elements in which one of the main electrode terminals is individually connected to both ends of the secondary coil and the other of the main electrode terminals is commonly connected to form one of the pair of DC output ends.
[0003]
The snubber circuit is a protection circuit for protecting the rectifying element of the rectifying circuit, and is usually composed of a CR filter in which a resistance element and a capacitor are connected in series. The high-frequency voltage component generated by high-speed interruption of the switching element of the inverter circuit and increased by the leakage reactance component of the transformer is suppressed by the maximum value by this snubber circuit and is not applied to the rectifying element, so that the rectifying element can be protected. it can.
[0004]
[Problems to be solved by the invention]
However, when high-power DC-DC voltage conversion is performed by the above-described conventional DC-DC converter, the high-frequency power consumed in the snubber circuit increases in proportion to the increase in output DC power, and the snubber circuit generates heat. The temperature rise was excessive, resulting in problems such as shortening the service life.
[0005]
In particular, when the snubber circuit is miniaturized or a single chip is formed into a module part by resin molding in order to perform high-density mounting of the circuit, this adverse effect has been increased.
The present invention has been made in view of the above problems, and an object thereof is to provide a DC-DC converter capable of reducing the size and extending the life of a snubber circuit for suppressing a high-frequency voltage of a built-in single-phase full-wave rectifier circuit. It is said.
[0006]
[Means for Solving the Problems]
According to the DC-DC converter of claim 1, both ends of the secondary coil of the transformer are connected to the DC output terminal through the rectifier element, and the series connection ends of the pair of partial coils constituting the secondary coil are a pair of DC outputs. The ground terminal is connected to the other terminal and electrically connected to the base plate.
[0007]
In this configuration, in particular, the snubber circuit connected to both ends of the secondary coil of the transformer is composed of a pair of CR filters, and the conductor forming the series connection end of both CR filters is interposed on the main surface of the base plate immediately below Contact through a conductor.
If it does in this way, since it becomes a circuit composition which bypass-connects a pair of partial coils of a secondary coil of a transformer for single phase full wave rectification with a CR filter, respectively, without reducing the high frequency voltage suppression effect of the snubber circuit, The heat generated in the snubber circuit is radiated well from the series connection end of both CR filters to the base plate through the intervening conductor to suppress the temperature rise, and this temperature rise significantly improves the problems such as shortening the service life.
[0008]
In this configuration, the conventional snubber circuit is substantially compared to a single component shown by an equivalent circuit in which one resistance element and one capacitor are connected in series. In addition, since two snubber circuit components are required, there is a concern that it may be disadvantageous in terms of cost, required space, and the like.
However, since the voltages of both partial coils of the secondary coil of the transformer are separately applied to both CR filters of the snubber circuit, the voltage applied to each CR filter is half that of the conventional one. The CR electrode area under the constant current density condition is halved. As a result, the size of the snubber circuit as a whole is almost equal to that of the conventional one.
[0009]
In other words, in this configuration, the secondary coil is conventionally connected by bypass at both ends of the secondary coil of the transformer having a neutral point, while the snubber circuit is half the size of this conventional snubber circuit. The two partial coils of the secondary coil are individually connected by bypass, and the series connection ends of both CR filters constituting the snubber circuit are directly connected to the base plate by an intervening conductor. In addition, the temperature increase can be reduced with a simple configuration without increasing the cost and reducing the high-frequency bypass characteristics.
[0010]
According to the configuration of claim 2, wherein further the DC-DC converter of claim 1, wherein the intervening conductor, because it includes a via-hole conductor filled in vias holes in the circuit board, create separate step increase or intervening conductor Thus, it is possible to save the trouble of fixing in place and performing electrical connection.
According to the DC-DC converter of the third aspect, the single-phase AC voltage is output from the secondary coil with the neutral point of the transformer to the single-phase full-wave rectifier circuit, similarly to the DC-DC converter of the first aspect. The snubber circuit is formed by connecting a pair of CR filters in series.
[0011]
In this configuration, in particular, the conductor forming the series connection end of both CR filters is arranged below the bus bar extending from the series connection end (neutral point) of both partial coils forming the secondary coil of the transformer. to contact through the intervening conductor. The bus bar may be formed by extending the partial coil itself.
According to this configuration, since the pair of partial coils of the secondary coil of the transformer for single-phase full-wave rectification is bypass-connected by the CR filter, similarly to the configuration of claim 1, the high frequency of the snubber circuit is obtained. Without reducing the voltage suppression effect, the heat generated in the snubber circuit is well radiated from the series connection end of both CR filters to the bus bar through the intervening conductor to suppress the temperature rise. It will be much improved.
[0012]
Further, as already described in the description of the configuration of claim 1, the cost and the size of the snubber circuit itself do not increase significantly.
In other words, in this configuration, the secondary coil is conventionally connected by bypass at both ends of the secondary coil of the transformer having a neutral point, while the snubber circuit is half the size of this conventional snubber circuit. The two partial coils of the secondary coil are individually bypass-connected, and the series connection ends of both CR filters constituting this snubber circuit are directly connected to the bus bar protruding from the neutral point of the transformer by an intervening conductor. Thus, the increase in temperature can be reduced with a simple configuration without increasing the size and cost of the snubber circuit and without deteriorating its high frequency bypass characteristics.
[0013]
In this configuration , the intervening conductor further includes a branched conductor portion that is formed integrally with the bus bar and branches.
According to the configuration of 請 Motomeko 4, via stationary conductor, because it includes a via-hole conductor filled in vias holes in the circuit board, a step increase or intervening conductor separately created and fixed in position, electrical It is possible to save the trouble of making a general connection.
[0014]
According to the configuration of claim 5 according to claim 1 further in the DC-DC converter of any of the description one of 4, both CR filter has a substantially equal AC impedance each other.
In this way, the high-frequency voltage bypass characteristics in both half-wave voltage periods of the single-phase AC voltage output from the transformer are balanced, so that a high-frequency voltage component having a complicated waveform accompanying the unbalance is applied to the rectifying element. Can be avoided.
[0015]
Note that the term “spatial relationship” such as “downward” in the present specification specifies a relative spatial relationship, and does not specify an absolute spatial relationship.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Preferred embodiments of the DC-DC converter of the present invention will be described with reference to the following examples.
[0017]
[Example 1]
A DC-DC converter device as an embodiment of the DC-DC converter of the present invention will be described with reference to a circuit diagram shown in FIG.
(Circuit configuration)
This DC-DC converter device is for converting the voltage from the main battery 1 for running energy storage of an electric vehicle to the auxiliary battery 2 for supplying power to the auxiliary device and the control device. Capacitor 4 is an inverter circuit formed by bridge-connecting four MOS transistors 4a, 6 is a step-down transformer, 7 is a snubber circuit, 8 is two diodes for full-wave rectification, 9 is a choke coil 10 and a smoothing capacitor 11 A smoothing circuit 12 is an integrated control circuit.
[0018]
The higher terminal of the main battery 1 is connected to the cable 13 through the input terminal 14, and the lower terminal of the main battery 1 is connected to the cable 15 through the input terminal 16.
The smoothing capacitor 3 is connected between the input terminals 14 and 16, the cable 13 is connected to the drain electrode terminals of the pair of MOS transistors 4a on the upper arm side forming the higher DC input terminal of the inverter circuit 4, and the cable 15 is the inverter circuit. 4 is connected to the source electrode terminals of the pair of MOS transistors 4a on the lower arm side forming the lower DC input terminal 4. The gate electrode of each MOS transistor 4a of the inverter circuit 4 incorporates a circuit for amplifying the input control voltage.
[0019]
A pair of AC output terminals of the inverter circuit 4 are connected to both ends of the primary coil 60 of the step-down transformer 6.
The secondary coil of the step-down transformer 6 is formed by connecting two partial coils 61 and 62 wound in the same direction in series. One end of the partial coil 61 extends outside to form a bus bar 17, and the partial coil 62. One end of this is extended to the outside to form a bus bar 18. The bus bar 17 is connected to one anode electrode terminal of the pair of diodes 8, and the bus bar 18 is connected to the other anode electrode terminal of the pair of diodes 8.
[0020]
The intermediate terminal 6a that forms the neutral point of the secondary coil of the step-down transformer 6 is grounded to the base plate 31 (see FIG. 2) through the bus bars 19-21.
The snubber circuit 7 is formed by serially connecting CR filters 71 and 72 composed of chip-like components equivalent to each other by an equivalent circuit in which a resistance element and a capacitor are connected in series, and the bus bar 17 is connected through a connection conductor 22. The bus bar 18 is connected to one end of the snubber circuit 7, and the bus bar 18 is connected to the other end of the snubber circuit 7 through the connection conductor 23. The serial connection ends of both CR filters 71 and 72 are grounded to the base plate 31 through the intervening conductor 73.
[0021]
The cathodes of both diodes 8 are connected to one end 24 of the choke coil 10, and the other end 25 of the choke coil 10 is connected to the higher terminal of the auxiliary battery 2 through the bus bar 26, the output terminal 27, and the output cable 28. Yes.
(Description of operation)
The control circuit 12 intermittently connects each MOS transistor 4a of the inverter circuit 4 until the voltage of the auxiliary battery 2 reaches a predetermined value by the input of a charging command to its input terminal (not shown), and the control coil 12 is rectangular in the primary coil 60 of the step-down transformer 6. A wave AC voltage is applied, whereby a full-wave rectified voltage is output between the cathode of the diode 8 and the bus bar 19, and the full-wave rectified voltage is smoothed by the smoothing circuit 9 and applied to the auxiliary battery 2.
[0022]
The smoothing capacitor 3 reduces fluctuations in the discharge current of the main battery 1 due to the intermittent operation of the inverter circuit 4, and the snubber circuit 7 absorbs a high-frequency surge voltage as a CR filter.
(Arrangement of circuit parts)
FIG. 2 shows an enlarged plan view of the circuit components described above.
[0023]
Reference numeral 30 denotes a circuit board having a substantially rectangular outer edge shape, and includes a notch 30a opened on the right side in FIG. 2 and a through window 30b opened adjacent thereto. The circuit board 30 extends above the aluminum base plate 31 in parallel with the aluminum base plate 31 at a predetermined distance from the main surface. The circuit board 30 is fastened by screws to an unillustrated column portion standing on the back side of the circuit board 30 from the aluminum base plate 31.
[0024]
The pair of diodes 8 are positioned below the bus bar 19 (back side) in the through window 30 and are fixed on the aluminum base plate 31 for cooling, and above the circuit board 30 from the through window 30 (on the paper surface in FIG. 2). Projecting away from the head).
The choke coil 10 is fixed on the aluminum base plate 31 for cooling in the through window 30 and protrudes above the circuit board 30 from the through window 30 as shown in FIG.
[0025]
The transformer 6 is also fixed on the aluminum base plate 31 for cooling, and protrudes above the circuit board 30 from the through window 30b as shown in FIG.
The smoothing capacitors 3 and 11, the control circuit 12 including an IC module, and the like are mounted on the upper surface of the circuit board 30 (partially omitted).
The bus bar 21 is fastened to a support protrusion 31 a erected on the main surface of the aluminum base plate 3 on the circuit board 30 side.
(Main part structure)
The structure of the main part of the apparatus of this embodiment will be described below with reference to FIG.
[0026]
Both ends of the CR filter 71 are soldered on the conductor patterns 30b and 30c formed on the circuit board 30, and both ends of the CR filter 72 are conductor patterns 30c and 30d formed on the printed circuit board 30. Soldered on top.
The conductor pattern 30 c is formed continuously with the conductor pattern 30 f on the back surface side of the circuit board 30 through the conductor pattern on the inner peripheral surface of the via hole 30 e provided in the circuit board 30. 30 g is a via hole conductor formed by filling the via hole 30 e with a conductive paste.
[0027]
The aluminum base plate 31 has a trapezoidal protrusion 31b erected toward the circuit board 30, and the top surface of the trapezoidal protrusion 31b is in close contact with the conductor pattern 30g.
In this embodiment, the conductor pattern 30c constitutes a series connection end of a pair of CR filters 71 and 72, and 30e and 30f and the via-hole conductor 30g constitute an interposing conductor as referred to in the present invention.
[0028]
The AC impedances of both CR filters 71 and 72 are set equal.
(Function and effect)
According to the above-described configuration, the snubber circuit 7 is constituted by a pair of CR filters 71 and 72 connected in series with each other, and the series connection ends of both CR filters 71 and 72 are brought into contact with the aluminum base plate 31 directly below the intermediate conductor. Therefore, while ensuring the performance of the snubber circuit 7, the heat of the snubber circuit 7 can be dissipated well to the aluminum base plate 33, and is attached to the single-phase full-wave rectifier circuit without complicating the manufacturing process. The temperature of the snubber circuit 7 can be reduced satisfactorily.
[0029]
Further, since the AC impedances of both CR filters 71 and 72 are set to be equal, the high-frequency voltage bypass characteristics in both half-wave voltage periods of the single-phase AC voltage output from the transformer 6 are balanced. A high-frequency voltage component having a complicated waveform can be avoided from being applied to the rectifying element.
[0030]
[Example 2]
Another embodiment will be described with reference to FIG.
In the snubber circuit 7 of this embodiment, a part of the side end of the bus bar 19 extending in parallel with the circuit board 30 is cut out directly above the conductor pattern 30c forming the series connection end of both the CR filters 71 and 72. Forming a branching conductor portion 19a forming an intervening conductor referred to in the invention, bending the central portion of the branching conductor portion 19a to the circuit board 30 side, bending the tip of the branching conductor portion 19a parallel to the circuit board 30, The branch conductor portion 19a has its tip end in close contact with the conductor pattern 30c.
[0031]
The branched conductor portion 19a may be in contact with the conductor pattern 30c or may be fixed with solder or the like. Reference numeral 19b denotes a notch recess formed in the side end portion of the bus bar 19 after the branching conductor portion 19a is cut off.
In this way, the heat of the snubber circuit 7 is dissipated to the bus bar 19 through the conductor pattern 30c and the branched conductor portion 19a, so that the temperature of the snubber circuit 7 can be further reduced.
[0032]
[Example 3]
Another embodiment will be described with reference to FIG.
In the snubber circuit 7 of this embodiment, the entire bus bar 19 is bent without providing the branching conductor portion 19a of the second embodiment shown in FIG. 4, and further, it is directly applied to the electrodes 7a at the ends of both CR filters 71 and 72. It is a close contact.
[0033]
In this way, heat can be radiated from the CR filters 71 and 72 to the bus bar 19 without going through the thin conductor pattern 30c, so that the temperature rise of the snubber circuit 7 can be further reduced.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing a DC-DC converter for an electric vehicle as an embodiment of the DC-DC converter of the present invention.
FIG. 2 is a plan view of the DC-DC converter device shown in FIG.
3 is a cross-sectional view of a main part of the DC-DC converter device shown in FIG.
4 is a cross-sectional view of an essential part showing a modified embodiment of the DC-DC converter device shown in FIG. 3. FIG.
5 is a perspective view of an essential part showing a modified embodiment of the DC-DC converter device shown in FIG. 4; FIG.
[Explanation of symbols]
7 is a snubber circuit, 30 is a circuit board, 31 is an aluminum base plate, 19 is a bus bar, 19a is a branched conductor (intervening conductor), 30e is a conductor pattern (intervening conductor), 30g is a via-hole conductor (intervening conductor), 73 is Intervening conductor

Claims (4)

A transformer (6) having a secondary coil composed of a pair of partial coils (61, 62) wound in the same direction and connected in series;
An inverter circuit (4) for intermittently controlling the DC voltage and applying a single-phase AC voltage to the primary coil (60) of the transformer (6) ;
A first rectifying element (8) having one end connected to one of both ends of the pair of partial coils (61, 62) connected in series and the other end forming one (24) of a pair of DC output ends;
A second rectifier element (8) having one end connected to the other end of the pair of partial coils (61, 62) connected in series and the other end forming one (24) of the pair of DC output ends;
A grounding base plate (31) connected to an intermediate terminal (6a) which is a series connection end of the pair of partial coils (61, 62) forming the other of the pair of DC output ends;
Wherein the circuit board protrusion erected toward (30) circuitry substrate (30) in close contact with the top surface being secured to said base plate (31) of (31b) from said base plate (31),
A snubber circuit formed by connecting a pair of CR filters (71, 72) connected between both ends of the secondary coil in series and mounted on the circuit board (30) ;
With
A conductor (30c) forming a serial connection end, which is a terminal connected to each other of the CR filters (71, 72) , is disposed on the top surface of the protrusion (31b) of the base plate (31) directly below the interposition conductor (30e). , 30f and 30g, 73) . The DC-DC converter according to claim 1, wherein
The intervening conductor, DC-DC converter which comprises a via-hole conductor filled in vias holes in the circuit board. A transformer (6) having a secondary coil composed of a pair of partial coils (61, 62) wound in the same direction and connected in series;
An inverter circuit (4) for intermittently controlling the DC voltage and applying a single-phase AC voltage to the primary coil (60) of the transformer (6) ;
A first rectifying element (8) having one end connected to one of both ends of the pair of partial coils (61, 62) connected in series and the other end forming one (24) of a pair of DC output ends;
A second rectifier element (8) having one end connected to the other end of the pair of partial coils (61, 62) connected in series and the other end forming one (24) of the pair of DC output ends;
A snubber circuit formed by connecting a pair of CR filters (71, 72) connected between both ends of the secondary coil in series and mounted on the circuit board (30) ;
A bus bar (19) extending parallel to the circuit board (30);
With
A conductor (30c) forming a series connection end that is a mutually connected terminal of both CR filters (71, 72) is an intermediate that is a series connection end of the two partial coils (61, 62) of the transformer (6). is disposed below the terminal said bus bar (19) extending from (6a), and contact through intervening conductor wherein the busbar (19),
Before SL intervening conductor, DC-DC converter characterized by comprising the said bus bars branching conductor portion of the immediate end was partially cutaway formed by bending the circuit board side (19) (19a). The DC-DC converter according to any one of claims 1 to 3 ,
The two CR filters have DC impedances that are substantially equal to each other.

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